Solana will switch to a new way of agreeing on blocks, called Alpenglow, on Wednesday, 21 Oct. The upgrade activates in epoch 1064, which the Solana Foundation expects to start at about 15:00 UTC, and targets finality in roughly 150 milliseconds, against about 12.8 seconds today.
Solana is a so-called proof-of-stake blockchain, a network secured by validators, the computers that check transactions and are paid in SOL to do so. Finality is the point after which a transaction can no longer be reversed. It is what an exchange or a bridge usually waits for before releasing funds.
Alpenglow replaces TowerBFT, the consensus system Solana has run since launch. Under TowerBFT, each validator’s vote is itself a transaction written into a block, and finality waits for votes to pile up across 32 slots. Alpenglow has validators message their votes to one another and combine them into a single certificate, which settles a block within one or two rounds of voting.
Anza, the developer firm that built the upgrade, gave a slightly earlier go-live time on X. Both times are estimates, because epoch boundaries depend on how fast slots arrive.
Post by @anza_xyz on X: https://x.com/anza_xyz/status/2110021831445156266
Anza put go-live at about 14:50 UTC after what it called 18 months of work. On its protocol page, the voting component, Votor, can settle a block in a single round when 80% of stake votes, or in two rounds with 60%. It is designed to keep working with up to 20% of stake acting maliciously and another 20% offline at once. TowerBFT tolerated under a third.
The handover itself is staged. The feature activates at the epoch boundary, and 5,000 slots later blocks stop carrying user transactions for a short window. Once 82% of stake signs off on a starting block, Alpenglow takes over. Anza expects the handoff to take hundreds of milliseconds.
Why it matters: this is the second big timing change on Solana this month. Block time was cut from 400 to 200 milliseconds in stages that finished in October, as we covered in Solana’s cut to 200-millisecond slots and in last Saturday’s Chain Check. That made blocks arrive faster. Alpenglow is about how soon they become irreversible.
Who has to change what
For people sending transactions, nothing changes. The Foundation says the virtual machine that runs programs, transaction formats and fees stay the same, and wallets keep working as before.
Validators have two jobs before epoch 1064. They must run a client, the software a validator operates, built on Agave 4.3.0, which means Agave, Jito-Solana or Harmonic Salsa. Firedancer and Frankendancer, two alternative clients, are not supported during the migration, so their operators have to switch.
They also need a balance of 0.8 SOL or more in their vote account, on top of the minimum the account must hold to stay rent-exempt. That money covers a new per-epoch charge, the Validator Admission Ticket fee. A validator that does not pay it cannot vote or produce blocks in the following epoch.
Data providers have the most rework. Vote transactions disappear from blocks, so transaction counts and throughput dashboards will drop sharply without any fall in real activity, the Foundation warns. Proof of History, Solana’s built-in clock, no longer paces block production either.
Alpenglow’s second half, Rotor, would replace the way block data is spread across the network. It is not yet scheduled. Other networks are reworking their base layer too: Aptos’s encrypted mempool, another base-layer change this week.
SOL was little changed at $106.54 as of 09:52 UTC, according to Kraken. The next milestone is epoch 1064 on 21 Oct.
This article is for information only and is not investment advice.